Proteomic analysis reveals allelopathic responsive mechanisms for para-hydroxybenzoic acid in poplars

The allelochemical para-hydroxybenzoic acid (pHBA) is a serious threat to poplars subjected to continuous cropping. In order to elucidate the responsive mechanisms of plants to pHBA stress, we here performed tandem mass tag-based quantitative proteomic analysis combined with physiological, transcriptional, and metabolic analyses by using H2O2 treatment as a positive control. H2O2 and O2•− levels and the activities of several antioxidant enzymes increased under pHBA stress. In total, 289 differentially expressed proteins were identified in the 84K poplar leaves under pHBA stress; among them, 161 and 128 proteins were upregulated and downregulated, respectively. The pHBA-responsive protein analysis showed that the antioxidant system, signal transduction, carbohydrate metabolism, biosynthesis of secondary metabolites, gene expression regulation, and many other biological processes were altered in poplars to cope with this stress. Overall, this study provides a new insight for the molecular mechanisms underlying pHBA stress in plants and may have potential application values in poplar genetic breeding for overcoming continuous cropping obstacles.